The splanchnic hepatotrophic factors are being localized by selective extirpation of the non-hepatic splanchnic organs and by seeing the effects of such extirpations upon liver structure, function, and the capacity for regeneration. A specific objective is to determine how diversion of hepatotrophic factors by portacaval shunt causes declines in blood lipids. A stimulatory substance in regenerating livers has been identified. The nature of this (SS) substance will be studied by purification techniques and by in vitro testing of the purified moieties with a monolayer hepatocyte culture technique.